If you let your cat outside in the Americas (or anywhere cats haven’t lived for thousands of years) unsupervised I’m going to assume one of the following is true: you don’t care if your cat dies, and/or you don’t care about wildlife. Even if you live in a place with zero predators, why the hell are you trusting a CAT with road safety?
Saying this as someone who grew up with parents that let our cats live (and die, a lot) that way. And as someone who has seen two friends lose cats to coyotes in the past year. And also interrupted an attack on someone’s pet by a coyote. It’s been a bad fucking year here for coyotes.
Plus, my (indoor) cat can't help but have a loud, boisterous conversation with any cat that wanders through my yard. Usually at 2am while I'm trying to sleep.
My cats were born an outdoor cat and I'd rather they touched some grass and lived an actual life rather than be stuck inside all day even if they die earlier. I'm sure they would too.
Wildlife argument is valid though. They kill some good (rats, mice), but I can't justify them killing birds and lizards.